Phthalonitriles are very versatile chemical intermediates and therefore are technically valuable compounds. Phthalonitriles are used to produce compounds which are important in the production of polymers for synthetic fibers, films and moldings, polyesters, polyimides and epoxy resins, rubber chemicals, agricultural chemicals and pharmaceuticals.
The reaction between alkylbenzene, ammonia and oxygen in the presence of a catalyst and methods for the preparation of appropriate catalysts are generally known (See, for example, U.S. Pat. Nos. 4,336,205, 4,284,781, 4,189,580). Also known are methods for preparing phthalonitriles by oxidative ammonolysis (ammoxidation) of xylene in the presence of a catalyst consisting of a mixture of metal oxides deposited onto a catalyst support. Specifically, the synthesis of phthalonitriles from xylenes by oxidative ammonolysis, including synthesis of isophthalonitrile from m-xylene using a catalyst composed of antimony oxide, bismuth oxide, vanadium oxide or molybdenum oxide, and ferric oxide on a carrier which is preferably silica gel or alumina has been described in U.S. Pat. No. 4,439,371.
The ammoxidation of m-xylene to isophthalonitrile utilizing a catalyst comprising a mixture of vanadium oxide and molybdenum oxide on an alumina carrier which is activated with at least one of cerium, chromium, manganese, tungsten, bismuth, tin, antimony, titanium, lithium, sodium, and potassium is described in U.S. Pat. No. 3,870,743.
U.S. Pat. No. 3,870,743 describes a method for preparing phthalonitriles by way of oxidative ammonolysis of xylenes at temperatures in the range of 300.degree. C. to 600.degree. C. and the contact time of 0.1 to 4 seconds.
A principal disadvantage of the above-discussed methods resides in an insufficient per pass conversion of the desired product and a low isophthalonitrile selectivity of the catalyst. Thus, improvements to the product per pass conversion and the isophthalonitrile selectivity of the catalyst would be welcome improvements to the art.
It is, accordingly, an object of the present invention to provide a catalyst for the preparation of isophthalonitrile from m-xylene by ammoxidation at elevated temperatures having improved product per pass conversion and increased product selectivity of the catalyst.